Received: 16 January 2019
Revised: 3 July 2019
Accepted: 11 July 2019
First Online: 23 July 2019
Compliance with ethical standards
: This study was approved by the Research Ethics Committee, Faculty of Medicine, Chiang Mai University (#033/2017). All participants and their parents provided written informed consent (Thai Clinical Trials Registry: TCTR20170209001).
: The authors declare that they have no conflict of interest.
: Written informed consent was received from parents or legal guardians of the children, and written assent was obtained from children over 7 years old prior to commencement of this study.
: All procedures performed in this study involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and the 1964 Helsinki Declaration and its later amendment or comparable ethical standards. This study was approved by the Research Ethics Committee, Faculty of Medicine, Chiang Mai University.